What characterizes anemia?

Anemia is characterized by a lack of a normal number of red blood cells or insufficient hemoglobin levels in the blood, which is integral for transporting oxygen throughout the body. The condition results in a decreased ability of the blood to carry adequate oxygen to tissues, leading to symptoms such as fatigue, weakness, and pallor.

The correct answer highlights that the fundamental issue in anemia is the deficiency of red blood cells, which can stem from various causes, including nutritional deficiencies, chronic diseases, or bone marrow problems. Understanding this is crucial for recognizing and addressing the various forms of anemia and their underlying causes, which can impact overall health significantly.